Project Summary: Neurodegenerative disorders are characterized by progressive loss of the neurons in the central nervous system eventually leading to permanent disability or death. An early detection of neurodegenerative disorder is crucial as it may allow timely intervention which can either cure or reduce the progression of the disease leading to a better clinical outcome. Currently, the diagnosis of most of the neurodegenerative diseases is based on clinical presentation and Imaging. However, at an early stage, imaging may not be conclusive. Blood-based diagnostics are of much interest for neurodegenerative disease because these are non-invasive, cost effective and ease of use. In spite of the advantages of blood-based diagnostics, there are not many FDA biomarkers approved for neurodegenerative disease use. Exosomes are a class of extracellular vesicles which are approximately 60-100 nm in size and are derived from host cell membrane. Several studies have shown that exosomes are released by the cells of the CNS including neurons, astrocytes, and oligodendrocytes which play an important role during the development, activation and regeneration of the CNS. Exosomes are known to pass through BBB under normal and pathological conditions making them an ideal source of CNS biomarkers which can be detected in blood. Further, due to the encapsulation in the exosomal membrane, the proteins, lipid, and RNA inside them are more stable and resistant to degradation. A major challenge in using exosomes as a tool for novel biomarker discovery in biofluids is to enrich exosomes from CNS. Serum and plasma contain a heterogeneous mix of exosomes which are released by several organs of the body. In this proposed study, our goal is to identify and enrich specifically neuronal derived exosomes (NDEs) from total exosomes in serum for a more sensitive and specific biomarker discovery. The two specific aims of this study are a) Identify and characterize neuronal cell specific marker on exosomes membrane in human cortical neurons in a cell culture-based assay. b) Validate the exosomal surface markers by enriching neuronal derived exosomes and evaluating them for biomarkers for traumatic brain injury. The proposed study for the first time proposes detection of TBI biomarkers using neuronal derived exosomes harvested from serum. The results of this study has potential implications for biomarker identification for other neurodegenerative disorders such as Alzheimer's, Parkinson's disease and chronic traumatic encephalopathy.